1. Field of the Disclosure
This disclosure relates generally to apparatus and methods for cutting or milling a casing or another element within a wellbore and retrieving cut elements to the surface.
2. Background of the Art
Wellbores are drilled in subsurface formations for the production of hydrocarbons (oil and gas). Modern wells can extend to great well depths, often more than 15,000 ft. A wellbore is typically lined with casing (a string of metal tubulars connected in series) along the length of the wellbore to prevent collapse of the formation (rocks) into the wellbore. Sometimes it is necessary to cut away part of the casing at one or more locations and then remove the cut portion to the surface. At other times it is necessary to mill one or more long sections of the casing. To perform a cutting and pulling operation, a tool with a cutter is typically conveyed into the casing to cut away part of the casing at a desired location. A spear, either as a part of a tool that includes the cutting tool or conveyed separately from the surface, is attached to the inside of the casing above the cut-away portion is then pulled uphole to pull the casing out of the hole. Currently available cutters are not capable of milling very large sections of a casing because cutting elements degrade to a level such that further milling is not feasible. Therefore, several trips are made into the wellbore with cutter replacements to mill long sections, which can result in excessive non-productive time. Therefore, it is desirable to have a tool capable of making multiple cuts in a casing or milling a long section or more than one section of a casing during a single trip into the wellbore.
The disclosure herein provides apparatus that includes more than one cutter that can be independently activated and deactivated to perform multiple cutting operations and milling long casing sections in a closed loop manner during a single trip into the wellbore.